The last 50 years have seen the emergence of childhood obesity as a major public health concern and a condition now regularly encountered in routine general paediatric practice. Causes are extremely complex, bringing together multifactorial environmental factors and individual genetics, and we still do not have a clear understanding of why some children appear predisposed to exaggerated and sometimes extreme weight gain. Overweight and obese children of today face an uncertain future. They are likely to experience higher rates of type 2 diabetes and heart disease, as well as many other health problems. However, while the prevalence of childhood obesity has progressively increased over the last few decades, so has research into its underlying causes. This has led to large-scale trials aimed at improving prevention or treatment. As data have emerged from such studies, we have begun to accept that the heterogeneity of obesity means that broad common sense' strategies to address diet and activity will not lead to success on their own. Now is the time to begin to build on this information, dispelling myths and beliefs, in order to focus research efforts and take first steps towards more sophisticated strategies that go beyond the surface behaviours that simply potentiate obesity. Through carefully designed studies, aimed at tackling fundamental questions missed in the hasty development of common sense' approaches, will come answers that can lead to the development of more effective community- and health-care-orientated prevention and treatment programmes.